ABSTRACT
Clinical development of catechol-based orthosteric agonists of the dopamine D1 receptor has thus far been unsuccessful due to multiple challenges. To address these issues, we identified LY3154207 (3) as a novel, potent, and subtype selective human D1 positive allosteric modulator (PAM) with minimal allosteric agonist activity. Conformational studies showed LY3154207 adopts an unusual boat conformation, and a binding pose with the human D1 receptor was proposed based on this observation. In contrast to orthosteric agonists, LY3154207 showed a distinct pharmacological profile without a bell-shaped dose-response relationship or tachyphylaxis in preclinical models. Identification of a crystalline form of free LY3154207 from the discovery lots was not successful. Instead, a novel cocrystal form with superior solubility was discovered and determined to be suitable for development. This cocrystal form was advanced to clinical development as a potential first-in-class D1 PAM and is now in phase 2 studies for Lewy body dementia.
Subject(s)
Isoquinolines/pharmacology , Receptors, Dopamine D1/agonists , Acetylcholine/metabolism , Administration, Oral , Allosteric Regulation/drug effects , Animals , Binding Sites , Crystallography, X-Ray , Cyclic AMP/metabolism , HEK293 Cells , Half-Life , Humans , Isoquinolines/chemistry , Isoquinolines/pharmacokinetics , Kidney/drug effects , Kidney/metabolism , Locomotion/drug effects , Mice , Molecular Conformation , Protein Isoforms/agonists , Protein Isoforms/metabolism , Rats , Receptors, Dopamine D1/metabolism , Small Molecule Libraries/chemistry , Small Molecule Libraries/metabolism , Small Molecule Libraries/pharmacology , Structure-Activity RelationshipABSTRACT
As part of our ongoing efforts to identify novel ligands for the metabotropic glutamate 2 and 3 (mGlu2/3) receptors, we have incorporated substitution at the C3 and C4 positions of the (1S,2R,5R,6R)-2-amino-bicyclo[3.1.0]hexane-2,6-dicarboxylic acid scaffold to generate mGlu2/3 antagonists. Exploration of this structure-activity relationship (SAR) led to the identification of (1S,2R,3S,4S,5R,6R)-2-amino-3-[(3,4-difluorophenyl)sulfanylmethyl]-4-hydroxy-bicyclo[3.1.0]hexane-2,6-dicarboxylic acid hydrochloride (LY3020371·HCl, 19f), a potent, selective, and maximally efficacious mGlu2/3 antagonist. Further characterization of compound 19f binding to the human metabotropic 2 glutamate (hmGlu2) site was established by cocrystallization of this molecule with the amino terminal domain (ATD) of the hmGlu2 receptor protein. The resulting cocrystal structure revealed the specific ligand-protein interactions, which likely explain the high affinity of 19f for this site and support its functional mGlu2 antagonist pharmacology. Further characterization of 19f in vivo demonstrated an antidepressant-like signature in the mouse forced-swim test (mFST) assay when brain levels of this compound exceeded the cellular mGlu2 IC50 value.
Subject(s)
Antidepressive Agents/pharmacology , Behavior, Animal/drug effects , Drug Discovery , Receptors, Metabotropic Glutamate/antagonists & inhibitors , Animals , Antidepressive Agents/chemical synthesis , Antidepressive Agents/chemistry , Brain/drug effects , Cyclohexanes/chemical synthesis , Cyclohexanes/chemistry , Cyclohexanes/pharmacology , Dose-Response Relationship, Drug , Humans , Male , Mice , Mice, Inbred Strains , Models, Molecular , Molecular Structure , Motor Activity/drug effects , Receptors, Metabotropic Glutamate/chemistry , Receptors, Metabotropic Glutamate/isolation & purification , Structure-Activity Relationship , SwimmingABSTRACT
Negative modulators of metabotropic glutamate 2 & 3 receptors demonstrate antidepressant-like activity in animal models and hold promise as novel therapeutic agents for the treatment of major depressive disorder. Herein we describe our efforts to prepare and optimize a series of conformationally constrained 3,4-disubstituted bicyclo[3.1.0]hexane glutamic acid analogs as orthosteric (glutamate site) mGlu2/3 receptor antagonists. This work led to the discovery of a highly potent and efficacious tool compound 18 (hmGlu2 IC50 46±14.2nM, hmGlu3 IC50=46.1±36.2nM). Compound 18 showed activity in the mouse forced swim test with a minimal effective dose (MED) of 1mg/kg ip. While in rat EEG studies it exhibited wake promoting effects at 3 and 10mg/kg ip without any significant effects on locomotor activity. Compound 18 thus represents a novel tool molecule for studying the impact of blocking mGlu2/3 receptors both in vitro and in vivo.
Subject(s)
Antidepressive Agents/chemistry , Antidepressive Agents/pharmacology , Depressive Disorder, Major/drug therapy , Glutamic Acid/analogs & derivatives , Glutamic Acid/pharmacology , Receptors, Metabotropic Glutamate/antagonists & inhibitors , Animals , Antidepressive Agents/pharmacokinetics , Bridged Bicyclo Compounds/chemistry , Bridged Bicyclo Compounds/pharmacokinetics , Bridged Bicyclo Compounds/pharmacology , Cell Line , Depressive Disorder, Major/metabolism , Dogs , Glutamic Acid/pharmacokinetics , Haplorhini , Hexanes/chemistry , Hexanes/pharmacokinetics , Hexanes/pharmacology , Humans , Madin Darby Canine Kidney Cells , Mice , Rats , Receptors, Metabotropic Glutamate/metabolismABSTRACT
A novel series of selective negative allosteric modulators (NAMs) for metabotropic glutamate receptor 5 (mGlu5) was discovered from an isothiazole scaffold. One compound of this series, (1R,2R)-N-(4-(6-isopropylpyridin-2-yl)-3-(2-methyl-2H-indazol-5-yl)isothiazol-5-yl)-2-methylcyclopropanecarboxamide (24), demonstrated satisfactory pharmacokinetic properties and, following oral dosing in rats, produced dose-dependent and long-lasting mGlu5 receptor occupancy. Consistent with the hypothesis that blockade of mGlu5 receptors will produce analgesic effects in mammals, compound 24 produced a dose-dependent reduction in paw licking responses in the formalin model of persistent pain.
Subject(s)
Amides/chemistry , Amides/pharmacology , Cyclopropanes/chemistry , Cyclopropanes/pharmacology , Receptor, Metabotropic Glutamate 5/metabolism , Allosteric Regulation/drug effects , Amides/pharmacokinetics , Animals , Behavior, Animal/drug effects , Cyclopropanes/pharmacokinetics , Glutamic Acid/chemistry , Glutamic Acid/metabolism , Indazoles/chemistry , Indazoles/pharmacokinetics , Indazoles/pharmacology , Male , Rats , Rats, Sprague-Dawley , Receptor, Metabotropic Glutamate 5/chemistry , Thiazoles/chemistry , Thiazoles/pharmacokinetics , Thiazoles/pharmacologyABSTRACT
The azetidinone LY307174 (1) was identified as a screening lead for the vasopressin V1a receptor (IC50 45 nM at the human V1a receptor) based on molecular similarity to ketoconazole (2), a known antagonist of the luteinizing hormone releasing hormone receptor. Structure-activity relationships for the series were explored to optimize receptor affinity and pharmacokinetic properties, resulting in compounds with Ki values <1nM and brain levels after oral dosing approximately 100-fold higher than receptor affinities.
